#region License
// Copyright 2008-2009 Jeremy Skinner (http://www.jeremyskinner.co.uk)
// 
// Licensed under the Apache License, Version 2.0 (the "License"); 
// you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at 
// 
// http://www.apache.org/licenses/LICENSE-2.0 
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, 
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
// See the License for the specific language governing permissions and 
// limitations under the License.
// 
// The latest version of this file can be found at http://www.codeplex.com/FluentValidation
#endregion

namespace FluentValidation.Validators {
    using System;
    using System.Collections.Generic;
    using Attributes;
    using Internal;
    using Resources;
    using Results;

    [ValidationMessage(Key = DefaultResourceManager.Equal)]
    public class EqualValidator<TInstance, TProperty> : IPropertyValidator<TInstance, TProperty>, IComparisonValidator {
        readonly Func<TInstance, TProperty> _func;
        readonly IEqualityComparer<TProperty> _comparer;

        //public EqualValidator(string identifier, Func<TInstance, TProperty> expression)
        public EqualValidator(Func<TInstance, TProperty> expression)
        {
            _func = expression;
            //Identifier = identifier;
        }

        public EqualValidator(Func<TInstance, TProperty> expression, IEqualityComparer<TProperty> comparer)
            : this(expression)
        {
            _comparer = comparer;
        }

        #region IComparisonValidator Members
        public Comparison Comparison {
            get { return Comparison.Equal; }
        }

        //public string Identifier { get; private set; }
        public object ValueToCompare { get; set; }
        #endregion

        #region IPropertyValidator<TInstance,TProperty> Members
        public PropertyValidatorResult Validate(PropertyValidatorContext<TInstance, TProperty> context) {
            TProperty comparisonValue = _func(context.Instance);
            bool success = Compare(comparisonValue, context.PropertyValue);

            if (! success) {
                MessageFormatter formatter = new MessageFormatter()
                    .AppendProperyName(context.PropertyDescription)
                    .AppendArgument("PropertyValue", comparisonValue);

                string error = context.GetFormattedErrorMessage(typeof(EqualValidator<TInstance, TProperty>), formatter);
                return PropertyValidatorResult.Failure(error);
            }

            return PropertyValidatorResult.Success();
        }
        #endregion

        protected bool Compare(TProperty comparisonValue, TProperty propertyValue) {
            if (_comparer != null) {
                return _comparer.Equals(comparisonValue, propertyValue);
            }

            return Equals(comparisonValue, propertyValue);
        }
    }
}